Radiant energy signaling system



1942- J. H. HAMMOND, JR v 2,272,839

I RADIANT ENERGY SIGNALING SYSTEM Filed Nov. 23, 1938 4 Sheets-Sheet l 4 INVENTOR 1 JOHN I AYs HAMMOND,JR.

Feb. 10', 1942.

J. H. HAMMOND, JR RADIANT ENERGY SIGNALING SYSTEM Filed Nov. 23, 1938 4 Sheets-Sheet 2 .YINVENTOR JOHN HAYS HAMMOND,JR.

1942. J. H. HAMMOND, JR 2,272,339

RADIANT ENERGY SIGNALING SYSTEM Filed Nov. 25, 1938 4 Sheets-Sheet s INVENTOR Feb. 10, 1942.

J. H. HAMMOND, JR

RADIANT ENERGY SIGNALING sx'swm Filed Nov. 23, 1938 4 Sheets-Sheet 4 m J N m VI mm M 5 Wu w o ww A z 2 IA H N 0v J Patented Feb. 10, 1942 UNITED STATES PATENT OFFICE RADIANT ENERGY SIGNALING SYSTEM John Haysllammoml, J12, Gloucester, Mass. Application November 23, 1938, Serial No. 241,894

16 Claims.

The invention also provides polarized receiving means which may be rotated so as to eliminate any undesired interference without interfering with the reception of the desired signal.

The present method accomplishes selectivity of r The terminals I3 and I4 are connected. to a'h'ori transmission against intentional or other inter:

ference by similar signals of the same carrier frequency and may be practiced with any type of communication such as continuous wave telegraphy or telephony, facsimile transmission, etc.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed. Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the 'manner of its organization may be better understood by referring to the. following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 illustrates schematically one embodiment of the invention as applied to a transmitting and receiving system for polarized waves;

Fig. 2 illustrates diagrammatically one form of transmitter for use in connection with Fig. 1;

Fig. 3 shows a modified form of a transmitting and receiving system;

Fig. 4 shows diagrammatically the circuits of a continuous wave transmitter which may be used in connection with Fig. 3;

Fig. 5 shows a modified form of signaling for use in the continuous wave transmitter; and

Fig. 6 shows diagrammatically the circuits of a continuous wave receiver which may be used in connection with Fig. 3.

Like reference characters denote like'parts in the several figures of the drawings.

In the following description and in the claims parts will be identified by specific names 'fbr convenience, but they are intended to be as generic in their application to similar parts as the art-will'permit.

Referring to the accompanying drawings and more particularlyto Fig. 1 a transmitter ill is provided with output terminals II, l2 and I3, M. The terminals II and I2 are connected to a vertical radiator consisting of a rod [5 which is mounted in but-insulated from a reflector l6.

zontal radiator consisting of a rod ll which is mounted'in but insulated from a reflector l8. The reflectors l6 and I8 may be of any suitable type, but are preferably of parabolic section and have the rods I5 and I! located at the foci of these parabolas.

The energies produced by the transmitter In at the terminals II, l2 and I3, M are of the same frequency and of the same nature as to modulations, keying, etc. but in general will be of different radio phase. The energy producedat the terminals II and I2 will be utilized to drive the vertical radiator 15 which produces a substantially vertically polarized wave shown diagrammatically by the sinusoidal line 20. The energy produced at the terminals I3 and M will be utilized to drive the horizontal radiator ll which produces a substantially horizontally polarized wave shown diagrammatically by the sinusoidal line 2|. It is to be understood that the reflectors l6 and I8 are not essential to the operation of the system but are used to reinforce the strength and polarization of the radiations. While the planes of polarization of the two, radiations 20 and 2| are shown to be vertical and hori zontal respectively, they may be produced at any desired angles by suitably mounting the radiators and reflectors.

The radiations 20 and 2| are both directed to a single collecting antenna system 22 which is shown as consisting of a rod 23 mounted in but insulated from a collector 25 which is preferably of parabolic form with the rod 23 mounted at its focus. The antenna system 22 is supported on a hollow shaft 26 which is rotatably mounted in a bracket 21 secured to a receiver 28. A wheel 29 is fastened to the shaft26 so that the antenna system 22 may be turned through a range of 180. The rod 23 is connected through the hollow shaft 26 and bracket 21 to the two input terminals 30 and 3! of the receiver 28 which is suitably designed for the reception of the type of signal" By rotating the produced by the transmitter. antenna system 22 the receiver 28 may be made to respond to the vertically polarized radiation 20 or to the horizontally polarized radiation 2| or in part to both.

Preferably the transmitter It! should be so arranged that at the receiver the vertically polarized radiation 20 differs from the horizontally polarized radiation 2| by electrical degrees, which maybe described as a circularly polarized radiation. Under these conditions the amount of signal from the transmitter 10 which actuates the receiver, 28 is independent of the angular setting of the collecting antenna system 22. The system. however, may be operated if there is not exactly 90 degrees difference of electrical phase tion's'at the receiver, as some energy will be received from the transmitter at any angular position of the collecting. antenna system 22.

In the operation'of the system the transmitter and receiver circuits are adjusted in the usual way and continuous wave, telephonic, facsimile or any privacy or selective system can be used with the circuits of the receiver 28' suitably coordinated with the circuits "of the transmitter ill. The amount of signal received from the transmitter ill will be substantially independent of the angular setting of the collecting antenn system 22.

Since interference in general is usually of plane polarized nature it is evident that by rotating the collecting antenna system 22 until its axis is perpendicularrto the plane of polarization ofthe" interference it is possible to eliminate this interference almost entirely without affecting the intensity of the desired signal from the transmitter it. It is thus seen that this arrangement provides a means of transmission and reception quite free from disturbances of plane polarized radiation. of the same frequency and general nature as those being conveyed, thus an added method of selectivity is provided over'and above any selectivity which may be provided by the nature of the transmitting and receiving circuits. Referring to Fig. 2 a transmitter circuit is shown which may be used for producing the The grids of the tubes 38 and 39 are excited in phase quadrature with the same intensity of signal by the use of input elements such as an inductance and a resistor 46 for the tube 38 and a resistor 41 and a condenser 48-for the tube 38. These input elements are so arranged that the input impedance of the tube 38, shunted by the inductance 45 in series with the resistor 48, represents a 4.5 degree inductive load, whereas the input impedance of the tube 39, shunted by the resistor 41 in series with the condenser 48,

represents a 45 degree capacitive load. These two load impedances are preferably equal numerically- Because of the diflerent loadings the center of the secondary of the transformer 31 is at radio frequency with respect to ground. In practice the numerical impedances of the input elements 45, 46, 41 and -will be small in comparison with the input impedances of the tubes 38 and 39 and therefore these input elements will be chosen of substantially the same numerical impedance at the frequency of operation. The overall load on the secondary of the transformer 3'! is a resistance load, but the A; C. voltage from the grid of tube 38 to ground will differ by 90' electrical degrees from the voltage from the grid of the tube 39 to ground.

The output circuits of the tubes 38 and 88 include the primaries of two transformers 58 and 5B which are shunted by condensers 52 and 53 forming two tank circuits 53a and 54. The secondary winding of the transformer 50 is conp or of the plane of polarization of the two radia nected to the terminals 1 I and ii of the transmitter I 8 and the secondary winding of the transformer 5| is connected to the terminals l3 and I4 of said transmitter. The output circuits oi the tubes 38 and 38 are energized'by a battery 55 which is connected in series with a condenser 56. Across the condenser 58 and in circuit with a choke 51 is the secondary ofv a transformer 58, the primary of which is shown as connected to a source 59 of modulating energy. When the modulating energy is operative, the carrier energy will in general not be keyed but will be continuously operative. The condenser 56 and choke 51 are used to minimize the flow of energy from. the tubes 38 and 39 to the modulation source 59.

The two tank circuits sad and 54 are tuned to the radio frequencyof the transmitter l5. As

a result of the phase quadrature relation of the grid excitation the plate circuits will also be actuated in phase quadrature, and both output cir. cuits will also be actuated by radio frequencies in phase quadrature, but not at 'a modulating frequency as represented by the output of the modulator 59.

It is to be understood that the circuit depicted in Fig. 2 is only illustrative and that any other suitable method could be used for producing the same results .and that the receiver 28 will be of suitable construction for responding to the system of communication which the circuits shownin Fig. 2 may be organized to create,

In addition to the superselective features achieved by the system depicted in Figs. 1 and 2 it is possible to use the two polarized waves for super privacy purposes by using a transmitter in which the relative phase of the radiations may be changed for purposes of/signaling and a receivingsystem by which the" phases of the radiations from the transmitter may be compared.

The general arrangement of such a system is shown schematically in Fig. 3. A transmitter 8|, of the samegeneral type as shown in Fig. l, is used for producing the two beams of polarized radiation but is provided with a means forshift-' ing the phase relations. The transmitter 6!, shown in plan view, is provided with the output terminals 82, 5 3, and 65, 68. The terminals 52 and 63 are connected to a vertical rod radiator. 6I which is located at the focus of a parabolic reflector 68. The terminals and 85 are connected to a horizontal rod radiator 69 located at the focus of a parabolic reflector III. The ver tical radiator 61 produces a vertically polarized wave indicated by the dotted line II and the horizontal radiator 69 produces a horizontally polarized wave indicated by the sinusoidal line 12.

A receiver 15 is provided with input terminals zontally polarized wave 12. Signaling is preferably of the continuous wave type, but wave am plitude modulation may be introduced as an aid to privacy if desired. Signaling is accomplished by changing the relative phases of the two radiations II' and 12 with the receiver I5 arranged so as tobc difierently responsive under the two conditions. v

A transmitter for producing the desired relative phase shifting is shown in Fig. 4 and is similar to the transmitter shown in Fig. 2 with the exception that keying means are provided for modifying the phase relations. A single phase source of carrier frequency energy is provided at 85 and is connected through a transformer 85 to the input circuits of two tubes 81 and 88, which are provided with a filament battery 89 and biasing resistor 90 the mid-point of which is .connected through condenser 9i and resistor 92 to ground. A suitable polarizing battery 93 and plate battery 95 are also provided. The output circuits of the tubes 81 and 88 are connected to two tank circuits 96 and 91 comprising condensers 98 and 99 and the primaries of two transformers I and IOI the secondaries of which are connected to output terminals I02, I03 and I05, I06 respectively which correspond to' the output terminals II, I2 and I3, I4 of Fig. 1.

Connected between the grids of the tubes 01 and 88 and ground are two resistors I01 and I08 and connected between these grids and the blades of a reversing switch I09 are two resistors Band III, the resistors I01 and I08 being greater than the resistors IIO and III. Connected between the contacts of the switch I09 and ground are an inductance H2. and a condenser II3. The impedances of the resistors IIO and III and of the inductance H2 and condenser H3 are about equal. The reversing switch I 09 is operated by a polarized relay I I the armature coil of which is connected to a reversing. switch H6. One pole of this switch is connected through two oppositely polarized batteries Ill and H8 to the blades of a double pole double throw switch II9. The left hand contacts of the switch II9 are connected to the contacts of a double acting'key I the armature of which is normally held in a central position. The right hand contacts of the switch II9 are connected to the contacts of a singleacting key I2i which is normally held in the up position.

In the operation of thetransmitter shown in Fig. 4 when the switch I I9 is thrown to the left the key I20 is put into operation. With the key in the central position as shown no current will flow-through the armature winding of the relay II5 so that the switch I09 will be held in the central position as shown. The paths from the grids of tubes 8'! and 88 to ground will then be through resistors I01 and I08 in which case the two grids will be excited in phase opposition,

these impedances serving to maintain'the grid bias and excitation under these conditions. The grid energy isthus repeated into the plate circuits and then through the tank circuits 90 and 91 and the transformers I 0| and I 02 to the two sets of output. terminals I02, I03 and I05, I 06 From these the energy passes to the radiators El and 69 shown in Fig. 3 where it is radiated as vertically and horizontally polarized waves, the phases of which are equal or in opposition according to the terminology arbitrarily set up for designating equality of phase.

When the key I20 .is depressed a circuit from the battery 'I I8 is closed through the armature winding of the relay II5 causing this armature of the relay II 5 to be moved to the left which in turn moves the switch I09 to the left. This causes the resistor I07 to be shunted by the reslstor H0 and inductance H2 and the resistor I08 to be shunted by the resistor III and condenser II3. This makes an inductive impedance from the grid of the tube 81 to ground and a capacitive impedance from the grid of the tube 88 to ground. This causes the phase of the radiation generated by the tube 81 to be advanced 45 electrical degrees and the phase of the radiation generated by the tube 88 to be retarded 45 electrical degrees, so that the radiation emitted by the radiator 61 leads the radiation emitted by the radiator 89 by 90 electrical degrees.

When the key I20 is elevated the battery III will be thrown in circuit with the armature winding of the relay II5, thus reversing the current through this winding and causing the armature to move to the rightthus throwing the switch I09 to the right. This will reverse the action just described and produce a capacitive impedance from the grid of the tube 81 to ground and an inductive impedance from the grid of the tube 88 to ground. This will cause the radiation emitted by theradiator 51 to lag 90 electrical degrees behind the radiation of the radiator 69.

When it is desired to use thekey I2I the double pole switch H9 is thrown to the right. Under these conditions a .circuit is normally closed from the battery III through the armature winding of the relay II5, which causes the switchI09 to be thrown to the right. This, as already? described, causes the radiation of vertically and horizontally polarized waves from the radiatorsB'I and-69 respectively, theformer lagging behind the latter by 90 electrical degrees. When the key IZI is depressed a circuit will be closed from the battery II8 through the armature winding of the relay I I5 causing the switch I09 to b thrown to the left, which," as already described causes the vertically polarized wave to lead by 90 electrical degrees the horizontally polarized wave. The action of the keys I20 and I 2| may be reversedby throwing the reversing switch H6 into the opposite position.

When operating the key I20 telegraphic code may be sent by using one position of the key for dashes and the other position for dots regardless of the extent of contact. With the key I2I operative dots and dashes are sent depending upon the lengths of time that the keyis depressed. The transmitter shown in Fig. 4 thus provides for both types of keying and the reversing switch,

key on one contact and with the opposite direction of rotation with the key on the other contact. A standard continuous wave receiver cannot distinguish any difierence between these two forms or polarization, while a suitably constructed receiver can so distinguish.

In case the radiations are not .jexactly circularlymolarized, but areelliptically polarized, it might be possible to distinguish between the two directions of rotation by the strength of the signals under the two conditions. For this reason it may be advantageous to provide in the carrier source a keyingarrangement for varying the carrierst-rength abruptly at dot and dash rates so thatthe true signals sent by the key I20 4 or key IZI cannot be distinguished on the basis of difierences of signal strength, but must be distinguished on the basis of phase relations.

Instead of using the abrupt keying arrangements shown in Fig. 4a continuous phase shifting arrangement maybe used as shown in Fig.5.

. rotation of the coil I21.

nals I82, I83 and I05, I86 as shown in that figure.

In Fig. 5 a three coil arrangement is provided which comprises two' fixed coils I and I26 coupled toa rotatable coil I21. The grid of the tube 81 is connected to the rotatable coil I21 and the grid of the tube 88 is connected to a tap on the fixed coil I26. Phase splitting circuits including two resistors I28 and I29 and a condenser I30 are connected to the fixed coils I25 and I26 and a single phase source of carrier frequency energy. I3! is provided which is similar to that shown at 85 in Fig. 4. The coils I25 and I25 are so arranged with their axes at right angles that they produce a'so-called rotating field analogous to that of a two phase induction motor in which the currents in the coils differ by 90 electrical degrees. The rotatable coil I21 is mounted in this rotating field and is opera= tively connected to a key I32 in such a way that when this key is depressed it will cause the coil I21 to be rotated in one direction and when it is elevated it will cause the coil I21 to be rotated in the. other direction. Stops I35 and I36 are provided so that the coil I21 is rotated through the desired angles when the key I32 is depressed or elevated. The arrangement of the circuits is such that-the voltages impressed on the grids of the two tubes 81 and 88 are substantially equal in magnitude regardless of the angular setting of the coil I21.

In the operation of the modified form of the invention shown in Fig. 5 the coil I21 may be so set that the tubes 81 and 88 are excited equally in phase when the key I32 is in a central position. When the key I32 is depressed the coil I21 will be rotated through the desired angle in the rotating magnetic field produced by the fixed coils I25 and I26 and will cause the waye generated by the tube 81 to' lead the wave generated by the tube 88 by an amount dependent upon the When the key I32 is elevated the reverse action will take .place and the wave generated by the tube 81 will lag behind the wave generated by the tube 88 an amount dependent upon the rotation ofthe coil I21. In this way the .keying may be accomplished by rotating the coil I21 in one direction for adash and the other direction for a dot.

Remote control of the'keying system maybe provided if desired.

- The difierence of electrical angular displace- .ment between the two waves need not be 90 electrical degrees'but may be much smaller, the minimum depending in part on the sensitivity of the receiving device .as a detector of phase shifts. In order to prevent the rotation of the coil I21 from being noted at an ordinary receiver because of any slight amplitude modulation or slight phase or frequency modulation which may be produced in the wave radiated by one -of the tubes 81 or 88, it may be desirable to vary the frequency, amplitude or frequency and amplitude of the carrier source I3I sufiiciently at keying rates so that as a practical matter the motion of the key I32.can be determined only by phase comparison of the two radiations.

' The receiver 15, shown in Fig. 3, which is used for receiving and interpreting the-two polarized waves H and "generated by the transmitter shown in Fig. 4 or that shown in Fig. 5 in conjunction with Fig. 4 may be provided witha re- 75 ceiving circuit as shown in Fi 6. In this circult the input terminals 16 and 11 are connected through a transformer I40 to a tuned circuit I4I which comprises the secondary of the transformer I49 and a variable condenser I42. The input terminals 18 and 19 are connected through a transformer I48 to a tuned circuit I which comprises the secondary of the transformer I43 and a variable condenser I46. The tuned circuits MI and I45 are connected to the first grids of two pentagrid mixer tubes I41 and I48. The

ground ends ofthese circuits are connected connected in the circuit of the secondary of the transformer I56. The second and fourth grids -of the tubes I41 and I48 are polarized by two batteries I58 and I59, while the plates of these tubes are further polarized by two additional batteries I60 and I6I which are connected through the primaries of two transformers I62 and I63 and through two radio frequency filters I65 and I66 to these plates. The fifth grids of the tubes I48 and I41 are connected to the cathodes, which may be self-polarized by two .cathode resistors I61 and I68 shunted by two condensers I69 and I18.

The secondaries of the transformers I62 and I63 are suitably tapped and connected through two resistors HI and I12 to the grids of two audio frequency amplifier tubes I15 and I16. Bridged across a part of the secondary of the transformer I62 is the resistor HI and an inductor I11 and bridged across part of the secondary of the transformer I63 is the resistor I12 and acondenser I19. The ground ends of the secondaries of the transformers I62 and I63 are connected to ground through two resistors I8I and I82 and the resistor I86 and battery I and are suitably by-passed by tyvo condensers I18 and I83. The plate circuits of the tubes I15 and I16 include two plate batteries I88 and I89 and the primaries of two transformers I 90 and I9I which are shunted by two resistors I92 and I93.

through a transformer 293 to a different tone source 285. The secondaries of the two transformers 2III and 283 are connected through a pair of head phones 206'to ground.

In the operation of the receiving system shown inFig. 6 use is made of the fact that if two waves of the same. frequency but of different/phase are both. heterodyned by the same source the resulting beat notes will have the same phase differonce as the -original waves and involves the use of two receivmg devices which are separately actuated by the two polarized waves and cause two audio frequency currents to be like phased or e 2,272,889 oppositely phased depending upon which wave leads the other by 90 electrical degrees.

When the two polarized waves 'II and 12 are received by the two rod antennas 80 and 82, shown in Fig. 3, the signals will be impressed upon the input terminals 16, 11 and 18, 19. From these terminals the signals will pass through the transformers I40 and I43 (Fig. 6) to the tuned circuits MI and I45 and will be impressed upon the first grids of the tubes I41 and I48. The input signals are heterodyned to audio or other low frequency by the oscillator I55 which impresses corresponding voltages on the third grids of the pentagrld tubes I41 and I48. The detected output currents from the tubes I41 and I48 will pass through the radio frequency filters I65 and I66 and 'will actuate the transformers I62 and I63 with audio or other low fre-.

constants. The. output audio currents arise from the term yeiea.

Let e1=m sin wt for the tube I41 e1=m sin (wt+') 'for the tube I48. Let ea=n sin t-p) t for both tubes where m and, n are constants, w and 1: refer to radio and audio frequencies and is the phase difference between e1 for tube I41 and er for tube I48. Then the audio currents are evaluated to'be i,==g cos pt for tube 147 i =fi 2n cos H-4,) f or tube 148 It is evident therefore that if the voltages im pressed on the grids of the tubes I41 and I48 correspond to those on the grids of the tubes 81 and 88 (Figs. 4 and 5) then the difference of phase of the audio currents at the transformers I82 and I63 will be the same as the differences of the radio phases. In place of comparing the radio-phases of the voltages it is only necessary to compare the phases of the detected currents. The audio circuits are so designed as to produce a phase shift of 45 electrical degrees in opposite senses in the two channels so that a net differential shift of 90' electrical degrees occurs in the audio circuits. As a result the audio currents become in phase with each other or outof phase with each other depending on which of the radio channels leads the other by 90 electrical degrees. This is accomplished by the phase shifting. circuits which comprise the resistor Hi and inductor I11 for the tube I15 and the resistor I12 and condenser I19 for the tube I16. These circuits advance by 45 electrical degrees the voltage impressed on the grid of the tube I15 and retard by 45 electrical degrees the voltage impressed on the grid of the tube I16. These voltages are amplified in the plate circuit of the tubes I15 and I16 and are impressed through the transformers I90 and ISI upon the combining circuit including the head phones I91 or the rectifier I98.

Automatic volume control may be used for making the voltage outputs of the transformers I90 and I9I substantially equal in magnitude. This may be accomplished by the signal currents which are rectified by the anodes of the tubes I15 and I16 from the grid transformer and which develop automatic bias voltage across the bias resistor I86 which is applied to the control grids of all the tubes. The battery I causes the automatic volume control to be inoperative unlessa satisfactory signal exists.

The rectified voltage developed across the resistor I86 is impressed through the resistors I81, I49 and I50, suitably by-passed and filtered by the condensers I83, I5I, I52 and I 53, to control the grid bias of the tubes I41 and I48, so that the audio voltages at the transformers I62 and I83 are a slowly increasing function of the signal voltages. The voltage across the resistor I86. supplemented by the voltage across the resistor I8I, controls the bias on the tube I15 and the voltage across the resistor I86 supplemented by the voltage across the resistor I82 controlsthe bias on the tube I18. In this way increasing signals at the transformers I62 and I63 decrease the gain ratios of the tubes I15 and I18. This volume control is so designed thatthe audio outputs at the transformers I90 and I9I are substantially the same and are of a definite amount regardless of'the total signal strength impressed on the two channels or of considerable difi'er- .ences of signal strength.

It is therefore evident that two substantially equal audio voltages result at the secondaries of the transformers I90 and I9I, the phases of which are dependent on the keying positions at the transmitter shown in Figs. 4 and 5. With the keys in the neutral position the voltages at the output sides of the transformers I90 and ISI will diifer in phase by 90 electrical degrees, but with the keys in the operative positions the phase difference of these audio'voltages will become zero or 180 degrees, depending on the position of the keys and the setting of the switch I I6 of Fig. 4. By operating the reversing switch I the outputs of the two transformers I90 and I9I may be made additive, for example when the key I20 is down, and subtractive when it is up. The two reversing switches IIS and I95 may be coordinated and synchronously thrown from time to time to change the correspondence of phases and signals as desired.

The selector switch I96 may be thrown to the left for indicating thecombined signals in the head phones I51 in response to the operation of the key I2I at the transmitter. With the key I2I in the down position the voltages combine to produce a loud signal and with the key in the up position the voltages oppose to produce a small or zero signal. For indicating in response to the operation of the key I20 at the transmitter the switch I96 may be thrown to the right; ,The signal will then be impressed on the diode rectifier I98 which will produce a direct current in the winding of the relay I99 the strength of which is controlled by the position of the key I20 at the transmitter. Thus when the key I20 is in the down position a strong current will pass through the winding of the relay I99 thus moving its armatur to the right which will close a circuit from the tone source 202 through the head phones'206 producing a given tone in these phones. When the key I20 is in the up position a weak current will pass through the winding of the relay I99 which will not be sufficient to opcrate this relay so that the tone source 205 will b thrown in circuit with the head phones 206 to produce a different tone in these phones. The relay I99 will be operated in a similar manner when the key I32 in Fig. is operated. It is thus seen that the position of the key I20 or the key E32 would be indicated by the tonal value of the sound in the head phones 20 6.

It is to be understood that the relative phases of the currents at th receiver may be compared in other ways than that described. For example the secondaries of the transformers I90 and I! may be connected to the deflecting plates of a cathode rayoscillograph yielding a circular diaa gram with the key l2!) in a neutral position, a vertical line when the key is down and a horizontal line when it is up.

Another method may use receivers in which an intermediate frequency circuit is placed between the radio and audio frequency circuits.

It is also to be understood that for receiving the waves generated by the system shown in Fig.

1 the audio outputs of the tubes H31 and M8 may be combined to make a so'-called rotating magnetic field in which may be mounted an adjustable,-rotatable secondary, suitably connected to an audio; amplifier. This. rotatable secondary would pick up the signals from the transmitter shown in Fig. 1 in any position, but for superselectivity purposesit would be so adjusted as to minimize the effects of any plane polarized radiation constituting interference Although only a few of the various forms in which this invention may be embodied have been.

shown herein, it is to be understood that the invention is not limited to any specific construction but may be embodied in various forms without departing from th spirit of the invention or the scope of th appended claims What is claimed is:

1. The method of communication which comprises propagating a plurality of plane polarized radio frequency waves displaced in phase by 90 in one direction and effecting signaling by producing a phase shift to 90" displacement in the other direction.

2. The 'method of communication, which comprises propagating a plane polarized radiant energy wave and signaling by periodically confverting said wave to a circularly polarized wave.

3. Th method of signaling, which comprises propagating circularly polarized radio frequency waves and signaling by periodically changing th direction of rotation of said waves.

4. The method of secret communication,

which comprises propagating a plurality of,

radiant energy waves, polarized in different planes, signaling by varying the phase relationship between said waves and masking the signal by introducing secondary modulations of said waves to conceal changes in characteristics produced by signaling.

5. The method of secret communication, which comprises propagating a plurality of radiant energy waves, polarized in different planes, signaling by varying the phase relationship between- '7. A system of radiant energy signaling comprising a transmitter having means to propagate a plurality of differently plane polarized,'radiant energy waves, means to alter the phase relationship of said waves for signaling purposes, a receiver having means to independently receive each of said .waves, said reveiver having indicating means actuated in accordance with'tne relative phase angles of said waves.

8. The system set forth in claim 7 in which th relative phase angle of said waves is shifted by 180 for signaling purposes. 9. The system set forth in claim '7 in whic automatic volume control means is provided to render the receiver non-responsive to changes in amplitude 'of the received waves.

10. The system set forth in claim 7 in which the phase differences are compared by heterodyning said waves with a common wave to a low frequency and comparing the phases of the low frequency waves.

11. A receiver for radiant energy, comprising a plurality of wave pick-up devices, responsive to waves polarized in difierentplanes, said receiver having channels actuated respectively by said picki-up devices, heterodyne means for heterodyning'each of said waves with the same heterodyne wave to a low frequency, phase changing devices responsive to th two low frequency waves and means actuated by the combined effect of said waves when said waves are of a given phase relationship and by the difierential effect of said waves when said waves are in other phase relationships to produce a signal according to the changes in relative phase.

12. Thesteps in a method of signaling which comprise producing a plurality of plane polarized radio frequency waves displaced in phase by thereby producing a rotary wavevector, and signaling by reversing the direction of said rotation.

13. The steps in a method of point to point signaling which comprise generating from one of said points two plane polarized radio frequency waves displaced in phase by 90, producing signaling energy displacing said phase in accordance with'saidlsignaling energy, transmitting the-. resultant energy, receiving the transmitted energy and deriving therefrom the signaling,

ene y I 14. The method of modulation which includes the .steps of producing polarized wave energy, producing other wave energy'of like frequency but of unlike phase and polarized in a different sense, diii'erentially phase modulating said wave energies in accordance with signals and radiating thev resultant polarized energies.

15. In a transmission system, a first aerial ar= ranged to radiate energy of a first polarization, a secbnd aerial arranged to radiate energy of a second polarization, means for impressing wave energies of like amplitude and frequency on said aerials and means for relatively phase modulating the energies so impressed in accordance with signals.

16. In a transmission system, a first aerial arranged to radiate energy of a first polarization, a second aerial arranged to radiate energy of a,

second polarization, means for impressing wave phases of said energies, and means for relatively accordance with signals.

phase modulating the energies so impressed in JOY-UNI HAIIMOND, JR. 

